The quantum electrodynamics called so because it unifies quantum physics and the electromagnetism (the latter being the unification of electricity and magnetism.
In short, quantum electrodynamics "to describe all the phenomena of the physical world, except for gravitational effects, and radioactive phenomena. That is to say that all phenomena involving light and matter are explained by this theory, explaining, among other things, the interactions between photons (light) and electrons (matter), hence the book title. This may seem abstract, but in reality, all phenomena that you know are from interactions between photons and electrons (except the gravity and radioactivity). These include all optical phenomena, but also biology and chemistry. Phenomena that may seem simple and explained that you thought were long in fact been definitively explained by quantum electrodynamics as the mere reflection and transmission of light in a glass slide that Feynman explains beautifully in the context of his theory . I will not go into detail as Feynman does it better than anyone else in his book but I would just like to talk a bit about the famous Feynman diagrams that can represent (and therefore understand) the interactions between particles.
Feynman diagrams
Feynman tells us that to "understand" quantum electrodynamics, you need a pencil, a sheet of paper and draw small arrows with a little savvy: is everything! The bet is quite ambitious at first sight, especially if the public has no academic training in physics but I think the bet was taken in this book (it takes still some scientific background, but the strict minimum allows to understand everything).
Feynman thus explains his theory by using several types of diagrams easy to build with a few simple rules. It begins with small arrows that represent events: for example an arrow can be a photon that travels from point A to B or a photon is reflected on a glass slide. Each arrow has a length representing the own probability of occurrence and the direction represents the time of the internal photon. Feynman says that the boom is running as a stopwatch and clock speed of rotation depends on the 'color' of the photon (the direction is the phase of the wave). All the little arrows multiply them to calculate the probability event of a more complex reflection and transmission in a thick glass slide. His eloquent demonstration is solving problems that have long remained mysterious, all with unprecedented accuracy.
He continued with another diagram where we represent the movement of electrons and photons that interact with each other in time and space ... It is question of emission and absorption of photons by electrons. It can be seen in the diagram below two different ways for an electron (solid line) to emit a photon (wavy line) which is then absorbed by another electron.
More generally, Feynman invented for practical matters a diagram that now bears his name: the famous Feynman diagrams. They are now used widely in what physicists call the quantum field theories (including quantum electrodynamics is derived) to perform calculations more easily. Simply make a small drawing in which one connects the points (called vertex) that are "events" with lines representing particles. These lines can be continuous, zig-zag, wavy etc. considered as particles for readability. We can represent these kinds of graphs chains decays and use it to make probabilistic calculations. Feynman diagrams allows us to reconstruct patterns of decays into other particles. You've probably heard of the famous Higgs Boson that the particle accelerator LHC at CERN should highlight. Well you can construct the Feynman diagram corresponding to the disintegration of 2 gluons in a Higgs boson, a top quark and anti-top quark in a collision in the LHC detector ATLAS. Here the result (though rather complex to understand):
You also know that physicists are small and have fun humor ... Special! A CERN physicist, John Ellis, has appointed a certain class of Feynman diagrams as penguin diagrams because of their form ... Judge for yourself:
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